Anisotropic conductive sheet process for producting the same, and circuit board inspection apparatus

Abstract

Disclosed herein are an anisotropically conductive sheet that can retain necessary conductivity over a long period of time upon its repeated use even when its thickness is small, and thus permits achieving high resolving power and long service life, a production process thereof, and an inspection apparatus for circuit boards equipped with this anisotropically conductive sheet. The anisotropically conductive sheet of the invention comprises a base material composed of an insulating elastic polymeric substance and a great number of conductive particles exhibiting magnetism, which are contained in the base material in a state oriented in a thickness-wise direction of the sheet to form chains, wherein an insulating reinforcing material formed of mesh is contained in the base material. The production process of the anisotropically conductive sheet of the invention comprises preparing a molding material with conductive particles exhibiting magnetism contained in a polymeric substance-forming material, which will become an elastic polymeric substance by being cured, forming a molding material layer containing a reinforcing material formed of mesh in a state immersed in the molding material, and subjecting the molding material layer to a curing treatment while applying or after an application of a magnetic field to the molding material layer in a thickness-wise direction thereof.

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       10 . An anisotropically conductive sheet comprising a base material composed of an insulating elastic polymeric substance and a great number of conductive particles exhibiting magnetism, which are contained in the base material in a state oriented in a thickness-wise direction of the sheet to form chains, and in a state that the chains by the conductive particles are dispersed in a plane direction of the sheet, wherein 
 an insulating reinforcing material formed of mesh is contained in the base material, and wherein a ratio r/R of a number average particle diameter r of the conductive particles to the average opening diameter R of the mesh is 0.01 to 0.9.    
   
   
       11 . The anisotropically conductive sheet according to claim  1 , wherein the mesh making up the reinforcing material is formed by organic fiber.  
   
   
       12 . The anisotropically conductive sheet according to claim  1 , which has a thickness of 20 to 500 μm.  
   
   
       13 . The anisotropically conductive sheet according to claim  1 , wherein a ratio of the thickness of the reinforcing material to the thickness of the anisotropically conductive sheet is 0.1 to 1.  
   
   
       14 . The anisotropically conductive sheet according to claim  1 , wherein an average opening diameter of the mesh making up the reinforcing material is 10 to 800 μm.  
   
   
       15 . A process for producing an anisotropically conductive sheet, which comprises the steps of. 
 preparing a flowable molding material comprising a polymeric substance-forming material, which will become an elastic polymeric substance by being cured, and conductive particles exhibiting magnetism contained in the polymeric substance-forming material,    forming a molding material layer containing a reinforcing material formed of mesh in a state immersed in the molding material,    forming chains by the conductive particles extending in the thickness-wise direction in the molding material layer in a state dispersed in the plane direction of the sheet by applying a magnetic field to the molding material layer in the thickness-wise direction thereof, and subjecting the molding material layer to a curing treatment while applying or after the application of the magnetic field to the molding material layer,    wherein a ratio r/R of a number average particle diameter r of the conductive particles to the average opening diameter R of the mesh is 0.01 to 0.9.    
   
   
       16 . An inspection apparatus for circuit boards, comprising the anisotropically conductive sheet according to claim  1 .